Structural modifications and immunoreactivity reduction of peanut allergen Ara h 1 under high-temperature and high-pressure processing

To elucidate the structural basis of allergenicity in Ara h 1, this study systematically investigated the effects of high-temperature and high-pressure (HTHP) treatments on both purified Ara h 1 and crude peanut protein extract (PE). Utilizing a combination of SDS-PAGE, ELISA, Western blotting, atomic force microscopy (AFM), circular dichroism, and intrinsic fluorescence spectroscopy, we demonstrated that thermal processing significantly induced protein degradation and conformational changes. Specifically, after treatment at 135 °C for 20 and 60 min, the immunoreactivity of purified Ara h 1 decreased to 33.4% and 16.7% of the control, respectively, whereas that in PE dropped to 25.0% and 10.0%. AFM imaging revealed a morphological transition from a globular structure to irregular short rod-like aggregates, accompanied by reduced size and increased heterogeneity. Spectroscopic analysis further showed increased exposure of tryptophan residues, an elevation in the proportion of random coils and α-helices, and the elimination of nearly all ordered tertiary structures containing tyrosine residues. These structural alterations were correlated with changes in physicochemical properties, ultimately leading to diminished biological activity and immunogenicity. It should be noted that these findings are based on immunoreactivity assessed with rabbit IgG and do not directly represent clinical allergenicity in humans.